text:
Why was this slightly unusual flight path followed?
I was just browsing the flight paths when I saw this:

(FlightRadar24: SN2825 from BRU to BUD on 26 Jul 2022)
But normally the path is straighter like this (not flying over Zurich):

(FlightRadar24: SN2825 from BRU to BUD on 25 Jul 2022)
I have seen even more deviation, like flying above Venice. This all adds some time to the total flight time.
Why is that? How can I know the reason?

Have you looked at weather maps and airspace closures at the time of the route?

Hi Akos, welcome to aviation.stackexchange. Please add the date of the flights to the question by using the edit function. WIthout knowing the date/time of these flight paths, it is going to be very hard to get a reliable answer.

I updated the date/time (without links), but the radar url's are also available now. Hopefully they remain accessible over time.

@RonBeyer well, that could be a sufficient explanation for me. Even if I don't find such a map (where can I view the weather at a given point in the past, or the airspace closures, without any subscription). I would never have imagined of closures or such 'bad' weather to make such detour anyways, especially because other flights didn't make that deviation. But sometimes it is even a larger curve, down to Venice as I mentioned.

This should explain it. Aircraft had to divert because of weather. this was the forecast for Thursday, but it was like this Tuesday as well.

I doubt that was the reason. We didn't have any rain yesterday in west Germany, e.g. Frankfurt reported 0mm rain yesterday (source). Also, other flights in a similar direction flew the normal route without the detour (e.g. SN2905 to Vienna).

Check out this screenshot from FR24's playback feature. There are many other aircraft in that area.

@Bianfable I would argue that that is neither how weather works, nor how airline dispatching works. Just because you didnt see the weather doesnt mean it wasn't there, and just because some airlines chose to go through/over the weather doesn't mean all will.

@Jamiec OK, maybe there was weather to avoid, but this answer doesn't show at all that this weather existed. The map is for a Thursday (tomorrow? last week?). I can't find a historical weather radar map of the region, but the forecast for 1500UTC (17:00 local) looked like this the evening before. Until evidence of thunderstorms is added to this answer, this is IMHO just speculation.

@Bianfable That I don't disagree with!

@Bianfable You don't have to have rain to be asked or told to divert for weather.  "I can't find a historical weather radar map of the region..." So let me know when you do. You also don't need to have thunderstorms to divert, because turbulence doesn't require a thunderstorm either. This is Private Pilot 101 stuff, not rocket science.


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Are standardized tail volumes used for swept wing GA aircraft like in straight wing designs? If so, what are they?
Are standardized tail volumes used for swept wing GA aircraft like in straight wing designs?
If so, what are they?
I understand that after roughly 100 years of aircraft design, there are rules of thumb/guiding principles to use regarding tail volume sizing.
As per the MIT open course notes for GA straight winged aircraft:
Horizontal Tail Volume: .3 -.6
Vertical Tail Volume: .02-.05
If applicable, what are the above tail volume values for GA aircraft with swept wings of roughly 20 deg?
Assumptions on stability/geometry of swept wing vs straight wing ( I stand to be corrected):

Pitch stability: the horizontal tail volume would be smaller as the swept wings provide added pitch stability.
Roll Stability: I'm told dihedral is a lot less then on straight wings, so better roll stability.
Yaw Stability: no idea

the ranges of those "MIT notes" should be setting off alarm bells, you need to figure distance from CG as well, yielding a $torque$ value.  Also, do you have 1 reason to sweep the wings of a GA plane back 20 degrees?

@Robert DiGiovanni: re sweep back - because it looks cool on an ultralight

Can't argue with that!  Maybe go with 5-7 degrees for starters.  It will help yaw stability.  But more sweep can create a dangerous pitch up on stall, as the wing tips stall first.  Washout will solve this, or slats, but separation of wing (lift) and tail (control), as in a Piper Cub is square 1.  Boring, but safe.

@ Robert DiGiovanni: Do you mean 5-7 deg sweep is better in yaw stability than 20 deg? Why is that?

no, adequate yaw stability is easily produced with flat sides and a vertical stabilizer, too many negatives in a 20 degree swept wing.  Just compare efficiency of straight wing to anything else.  In terms of safety, a highly swept wing would be 3rd, behind delta.

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Would using a full span spoiler and a separate flap be a better design than a flaperon for a STOL ultralight?
Would using a full span spoiler and a separate flap be a better design than a flaperon for a STOL ultralight?
I understand many ultralights use 50% flaps and 50% ailerons.  The problem with this, is that it greatly reduces your Clmax.
I understand Zenith uses a full length combination flap and aileron, called a flaperon.  However I imagine using the 50% split aileron with full flap would still effect total lift.
What about using a 100% spoiler and a separate 100% flap?  Would that be a better design?  If not, why not?
See pic below

Spoilers are so called because they spoil, that is cancel, lift.

Better how? VTC as opinion based.

you must define "better". cheaper? less drag? more strength?

@qqjkztd given the OP precise the question is about STOL, maybe take off performance (minimize stall speed, increase lift at low speed (e.g. with bigger flaps producing more drag as side effect)) is what the OP what to optimize. As this is about ultralight, maintenance cost and complexity can also be what the OP want to optimize.

"Most airplanes use 50% flaps and 50% ailerons" [citation needed]

Simplicity often makes the design lighter. If you have multi-purpose flaps, e.g. an inner and and outer flap, you can use the inner flap for creating a lot of lift and have the outer flaps droop down with flaps up to a certain point but still act as roll surfaces. If you just add spoilers on top they do nothing but roll control and are not as efficient as ailerons, they mostly add dead weight for 99% of the flight. With that design you can deflect the inner flap even further for landing whilst keeping the ailerons normal. Adds better control response at low speeds.

There is an interesting NACA report on use of spoilers for roll control here.
I think if you want to do that the spoiler should just be around the outer 1/3rd of span (the rolling moment generated inboard is low - barely worth extending the surface inboard. And the spoilers should be at the rear spar.  For reasons I'm not entirely clear on, they work much better close to the trailing edge and the only time you see spoilers at the main spar is on gliders where they are being used only to increase sink rate.
A significant downside to roll spoilers you have to account for is a "dead zone" in the first, say, 10 degrees of extension due to it having to extend beyond the boundary layer to start to work, so you find the stick also has a dead zone a bit to each side of center.  This may be why you don't see more use of roll spoilers on ultralights and airplanes that have airfoils that are fairly turbulent aft of the spar.
On the  other hand, the report says, to my surprise, that roll authority is almost as good while in inverted flight (I guess in that case it acts like a split flap when the pressure distribution is flipped over and is able to move the wing while inverted in the same direction as while right side up - this is the first report I've found that directly addresses this).
I'll also point out that the use of roll spoilers and full span flaps is usually done on airplanes where you want to maximize the speed range like on the MU-2, where you have very large fowler flaps that increase the wing area by about 20% by being full span.  In the end, for an ultralight that flies down to 25mph and cruises at 55 mph, all that trouble to develop full span flaps and roll spoilers might only get you a couple mph reduction at the bottom compared to a large flap and smallish aileron at the tip, with negligible benefit at the top.

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How does washout increase static pitch stability in subsonic swept wings?
How does washout increase static pitch stability in subsonic swept wings, more specifically in slow moving aircraft (eg. ultralights), 15mph to 60mph?
I understand washout is used to delay full stalls ( at least in unswept wings), but isn't pitch stability related to cg and centre of pressure?
See picture below of a european designed Archon SF1 rg ultralight with swept wings and retractable landing gear. Mid engine single prop is shown forward of the twin vertical tails.

Does this answer your question? How does the location of a propeller affect an aircraft's stability?

Here is one who is not interested in motor glider-like fuel efficiency!  Re Zeus comment: if you have retractable slats on a swept wing you move your center of lift back, allowing CG to be further back.  When slats are retracted, you can cruise without tail downforce saving fuel.  The washout is opposite, so designing washout in a swept wing will move the center of lift forward.  The secret is that center of lift on the WING generally moves forward with increasing AOA  so a "horizontal stabilizer", something to counteract this, must be added.

@Manu H: I'm not asking about the affect of prop location on stability. The pic just shows the only ultralight that I know that has swept wings. I'm interested in finding out how to make swept wings more stable in pitch. I was told that washout helps. Just wasn't sure how that works.

@Fred-- many ultralights have swept wings-- see https://en.wikipedia.org/wiki/Pterodactyl_Ascender -- note that variants have been flown with or without the canard-- the original Fledge/Pledge hang glider version had no canard-- undoubtedly this wing did have some washout--

related: How does wing sweep increase aircraft stability?

@Fred -- the discussion about whether the washout actually causes pitch stability, or just allows the CG to be moved forward, is a subtle one-- from the hang glider viewpoint we are sometimes interested in what happens if the aircraft goes weightless and the hang strap goes strap, effectively removing the pilot's weight from the picture-- this is when the pitch-up tendency delivered by washout is critical-- also for recovery from a very steep dive-- but I'm not saying any of the other answers are technically wrong--

@Fred -- all of the Rogallo-descended (but now highly evolved) swept or delta wings used on "trike" ultralights (basically a hang glider with a motor, seat, and wheels added) have very substantial washout, and it plays a key role in their pitch stability dynamics

(Make that "Pfledge" not "Pledge"!  Also "strap" (second occurence) should have been "slack")

@ quiet flyer: re trike ultralights- What is the typical angle of sweep and how much washout are you talking about? 2-3 deg? I understand on unswept wings, -1.5 deg washout is typical.

@Fred -- way more than 2-3 degrees of washout, I'm guessing at least 10.  Or maybe much more.  Maybe 20 or more.  Just a wild guess at present, haven't looked at drawing lately.  it's really pretty extreme.  See for example https://www.youtube.com/watch?v=-qA6pN1aeZ4 -- compare the angle of the metal rods at the tip, with the metal tube at the centerline.  What we would see in a trike ultralight might be similar.

Since its earliest days during the pioneer era, washout on a swept wing has been accurately described as "putting the tail at the end of the wing." It works in exactly the same way as a tail stabilizer.
As long as the change in moment of the rear surface is greater than the change in moment of the forward surface the plane will be statically stable. It matters not whether the tail is inboard, outboard, moved ahead of the wing (as a canard), tacked on the end of a swept wing, or even tacked on the back of a straight wing in the form of a reflex trailing edge.
On a straight, unswept wing washout can delay the stall a little, but stalling is a complex subject and best treated separately.

Washing out the outer span (i.e. decreasing the geometric incidence of the local section) of a swept wing does not directly increase the static stability of the aircraft (see addendum). The analysis mentions flying wing, but is applicable to any swept wing.
1. Stability
Static stability of a low-speed and structurally rigid flying wing is defined by having a negative variation of pitching moment with increasing angle of attack ($C_{m_\alpha}<0$), and is primarily achieved by the planform and the airfoil distribution:

Planform: the swept outer span offsets the aerodynamic center aft, just like a traditional tail.
Airfoil: the use of reflex airfoil allows for smaller unstable pitch variation at quarter chord, which further improves stability.

I'm going to skip why a negative pitching moment slope is necessary for static pitch stability, as this has been well discussed here (e.g.). Since the swept portion is (hopefully) aft of the CG, washout acts like a tailplane incidence and plays very little into stability.
2. Trimmability
However, stability is not the only concern. Trimmability is the other (some may argue even more important) issue: at the desired wing lift (or angle of attack), we must ensure that the total pitching moment is zero. This is shown graphically below, where a fully trimmed state is point A:

Image ref: Etkins, Dynamics of Flight
Traditionally this is achieved via pitch surfaces such as tailplane incidence and elevators (by shifting the above $C_m$ curve up and down such that point A can lie at the desired angle of attack). For a flying wing, elevons can be put to use. But it's less effective due to shorter moment arm. If the pitching moment is too negative, we may run out of available elevons to trim or left to maneuver.
Help can come from two sources:

Airfoil: reflex airfoil generally has positive pitching moment at zero angle of attack. This decreases the overall pitching moment of the wing.
Washout: since the swept portion is (hopefully) aft of the CG, it effectively acts like a negative incidence on the tailplane, alleviating elevons travel.

With washout, a larger range of forward CG becomes possible due to elevons alleviation. This indirectly helps with stability if the static margin of available CG range had been too small without the proper washout.
3. Addendum
Since washout modifies the lift distribution on the wing, it changes the downwash on the outer span ($\frac{\partial{\epsilon}}{\partial{\alpha}}$), which does affect stability. However, this effect is secondary to what had been mentioned.

Washout has been used to achieve stability since 1904 and was a principal feature of the first certified stable aircraft, flown in 1910. It has been used for this purpose on many aircraft since. Your initial claim is wholly without foundation. Think of washout as adding a lateral element to the airfoil distribution - an aspect you have not addressed.

@Guy Have you even read my whole post?

You can qualify your claim with as much stuff as you care to, it does not alter that fact that "Washing out the outer span (i.e. decreasing the geometric incidence of the local section) of a swept wing does not directly increase the static stability of the aircraft" is just plain wrong. Adding that "washout acts like a tailplane incidence and plays very little into stability" implies that tailplanes contribute little to stability, which is equally wrong. And yes, if I had not read your post I would not have known that you fail to mention lateral redistribution of the airfoil.

@GuyInchbald Did I say tailplane does not affect stability? I'm pretty sure there's the word "incidence" somewhere in that sentence. "You can qualify your claim with as much stuff as you care to", so no matter how many equations or authoritative references I find, there's no convincing you?

Yep, you'll find the word "incidence" copied in my quote. But if you can find a reliable authority who claims that tailplane incidence does not affect pitch stability, I will find ten who claim that it does.

@GuyInchbald How about you start with one reference that says, changing the tailplane incidence changes the stability characteristics of the airplane. I bold stability because I don't mean trim or trimmability.

First book on my shelf. A.C. Kermode; "Mechanics of Flight", Pitman, 1972. pp. 269-70. Explicitly mentions both washout and tailplane incidence as significant factors affecting longitudinal stability. Your turn now.

@GuyInchbald Had you read the first paragraph on Longitudinal Stability, you would've realized the author is, in fact, talking about trimmability. "We have seen that an ordinary unswept wing with a cambered aerofoil section cannot  be balanced...and at the same time be stable...". See this page for illustration of tailplane effect on Cm. As you can see, Cma is exactly the same across the different lines.

@GuyInchbald Or you can pick up "Dynamics of Flight", Etkins, 1996. The second chapter has all you need to know, especially Figure 2.16 (illustrated with elevator, but same idea with tailplane incidence). If you don't trust the equations, you can also pick up AVL; it has a B737 model you can readily load. Try different tailplane incidences and see for yourself how much Cm slope changes.

Well, "the author is, in fact, talking about trimmability" might be more believable if he had not headed the subsection Longitudinal Stability. I think I'll just leave you to your imaginative interpretations of what others actually write.

@GuyInchbald I encourage you to either write down the longitudinal equations and see what effect tailplane incidence (it) has on the stability derivative, or try out the vortex lattice method I mentioned before. Don't take my word or anyone else's; let the math do the talking.

"But the aeroplane does these things. And if the theory does not give warranty to the practice, then it is the theory which is wrong." -- J.W. Dunne, lecture on The Theory of the Dunne Aeroplane to the Aeronautical Society of Great Britain, 1913. My advice to you is to lift your eyes and ask a real aeroplane designer what those equations actually mean.

@Guy, consider it a terminology issue, but the truth is, the tail incidence (or swept washout) by itself indeed doesn't create stability. It is a consequence of the need to balance (trim) the aircraft. Yes, it so happens (and it can be easily shown) that for a stable aircraft you will normally need a relatively lower tail incidence (or negative twist/washout), but what creates stability (i.e.: "negative pitching moment slope") in the first place is having a tail (or a certain wing shape).

@Zeus, that is back to front. You can trim a tailless straight wing with a conventional airfoil but it will still be unstable. The tail brings stability, for which its incidence must be within a narrow range. If the wing is in trim, the tail has zero incidence and does not contribute to trim, but does bring stability. The trim range dictates the CG range of the craft, not the other way round. Designers often work backwards from the desired CG range and that is how the subject is all too often taught - practically, but backwards.

It works the same way as a tail, the wingtips are further aft, so the pitch torque around the center of gravity is greater.  $Torque$ = force x distance.

Yes, pitch stability is related to CG and center of pressure

To create "static pitch stability", the goal is to move the center of pressure further back with increasing AOA, which helps lower the nose.  The most common way do this is to move weight forward and have a down lifting tail, but this is not the only way.
One can make lift nuetral, or even down lifting wing tips on swept wings. As AOA increases, lift here becomes increasingly positive.
So you can wash out the wing tips, and they will start pushing the nose down if AOA gets too high, just like a horizontal stabilizer/elevator does.
As AOA increases, tail "downforce" goes to 0 downforce, then to "upforce" lift, moving the center of pressure further and further back.  This  safeguards the wing from reaching stall AOA.
One of my mentors told me "the wing is the symphony, the tail is the conductor"
With out a "tail", wing center of pressure typically moves forward with increasing AOA, which is "bad".

The 2nd paragraph is incorrect. The wing tips without washout (like the tail without decalage) would have even more nose-down moment (until they stall, but we are talking about normal flight). The point is that they actually provide (comparatively) nose-up moment, which allows to move CG forward, creating a stable configuration overall.

@Zeus ??? "They provide nose up moment, which allows to move CG forward"???  Isn't that what got Max into trouble?  Moving weight to solve an aerodynamic issue is "bad".  When u washout swept wings, lift is balanced with CG, lift moves back, instead of forwards because of longer lever arm at higher AOA.  In this respect, a longer fuselage and smaller downlifting tail is more efficient, with lower drag.  Washed out swept wings worked for Dunne, and are good for futuristic looking models, but do not allow for optimal wing AOA across the entire wing.

More scientificly put, if you wash out a swept wing pitch down torque increases as the longer lever arm of the wing tip begins to contribute lift force at a higher AOA. In the unstalled AOA range, increase in Coefficient of Lift is linear.  So, the center of lift moves back.  This is exactly what a properly designed H stab does,

@Zeus I think you mean to say the nose up moment from the washout creates a more trimmable configuration? I don't really see how washout affects stability (Cma) by a great deal.

Stability is not just an 'aerodynamic issue'; it's a balance issue as well. Pitch stability margin is the distance between CG and aerodynamic centre (or neutral point) for the whole aircraft. If you add washout or reduce tail AoA, lift moves forward, of course (and it has to be balanced with CG). But I guess you wanted to say that lift increase as AoA increases shifts back; this is equivalent to say that AC moves back. This is what I meant: now, with this arrangement, you can have CG in front of AC, which is the whole point.

@JZYL, this is all about swept wings. For them, washout has the same effect as lower AoA on the horizontal stabiliser, and it works for stability just the same way.

@Zeus Changing hstab angle hardly changes stability. It just shifts the Cm curve of the whole aircraft.

By itself, yes. This is why I started from CG and balance. This shifted Cm allows you to move CG and get a different stability picture.

If tail downforce changed to upforce, your stab wouldn't be leading edge down at low speed.  The slower you go, the higher the main wing AOA, for trim, the lower the stab's leading edge must go.  On no aircraft anywhere does the stab LE move up as you trim for a lower speed/higher AOA, which would have to happen if the tail was lifting up.  If the tail is making upforce, it means the C of G is aft of the Neutral Point and the tail lifting up to keep the nose from rising. This is an unstable condition.

But we could say "you change trim by using elevator to save stall", I'm working on preventing them in the first place.

Let's just say that if you remove the washout from my hang glider, I won't offer to test fly it  for you to see how it affected pitch stability.  Because I know it would have no pitch stability remaining at all.  And by the way I have verified that the washed-out tips create positive lift at low airspeed, and negative lift at high speed.  Just as does the horizontal tail of an aircraft with a moderately-far-aft CG location.

@quiet flyer Good comment, they "create lift at low airspeed" at higher AOA and "create negative lift at higher airspeeds" at lower AOA just like a tail.  The only issue of an uplifting tail vs a down lifting tail is (the same) uplifting tail stalls easier with increasing AOA.  Birds and XB-70s solve this by using a delta shaped "tail" that stalls at a much higher AOA.  So lifting tails are ok, as long as this parameter is under control.


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Can free flying twin drag rudders be mounted on a stabilator, aerodynamically speaking?
Can free flying twin drag rudders be mounted on a stabilator on an ultralight, aerodynamically speaking, or would it be disadvantageous?
I understand free flying rudders need up to 40% less area than a classical vertical tail arrangmenent with a stabilizer and rudder. Source: Zenith, Flying on your own Wings
I also understand that stabilators  need up to 15% less tail volume than a horizontal stabilizer and elevator.
Source: http://www.ae.metu.edu.tr/~ae451/geometry_sizing&configuration.pdf
I also understand an H-tail can be used as end plates to increase the effectiveness of an elevator by changing it's lift distribution, from an elliptical one to a rectangular one, reducing the elevator area required even more.
I also understand that twin drag rudders are more effective than standard
rudders in a twin rudder configuration, reducing the required area even more.
What about combining the two?
Can twin free flying differential drag rudders be mounted on the end of a stabilator?
See pic below.

The question is a bit vague and too general.  Are you asking whether it is physically possible, permitted by the FAA, economically feasible, aerodynamically advantageous, or...?

What is a free flying rudder?

@Super I googled for it and didn't find anything so I assume it's invented by OP, hence asking for clarification in the comments has a higher chance of success.

@ Super: A free flying rudder is a rudder without a vertical stabilizer. They have been around a long time. See Zenith 701.

@user3528438 Sorry about that. I didn't correctly interpret your meaning, it was a fault on my end.

@Fred I believe your comment is directed toward user3528438

@Fred The modern term seems to be "all-moving" or "all-flying" although I'm more familiar with "all-moving". All moving rudder in a H configuration will be very awkward structurally. E-2/C-2 is probably the largest rudder to stabilizer ratio you can get.

@user3528438: What is E-2/C-2?

@Fred Grumman E-2 Hawkeye/C-2 Greyhound

@qq jkztd: Why do you say the end plate stabilator would have to be one piece? Wouldn't it just be like wing tip rudders?


text:
How do contemporary Russian jet engines compare to Western ones?
How do contemporary Russian aircraft engines like the PS-90A1 and PD-14 compare
to similar engines from GE, PW, Rolls Royce and CFM International? How many years/generations they are behind their Western counterparts from aforementioned companies? In what ways exactly they are behind?

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What regulation allows airlines to require flight attendants to work up to 20 hours?
What regulation can a Part 121 airline use to bypass the rest requirements for flight attendants?
Our airline has been working flight attendants for up to 20 hours using the term "irregular operations". For example: "oops, the pilot is late"; "oops, there's bad weather"; "oh, you're at your home but we still need you to make that last leg even though you will be over your hours by 3 hrs". What regulation allows this?

The question in the header and the one in the body are actually different questions with different answers. 121.467(b)(14) allows for extending duty time “due to circumstances beyond the control of the certificate holder.” But bypassing rest requirements is not allowed. This legal interpretation from 2005 refers to a “long held FAA position that circumstances beyond the control of the certificate holder permit exceeding duty period limitations but does not permit reducing required rest periods.”

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Do you need type ratings for private flying?
This question popped into my head when I learned some Citation X series have shared (?) type ratings.
So a theoretical situation:
I am a happy person with PPL and IFR ratings and then I decide to rent a 737-800 to give a birthday party to a close friend.
Can I just charter a private jet (assuming I am lucky enough to find a company that will give one to me) and fly? Do civilians need type ratings? I have heard you need a type rating to be the pilot in command. (It wouldn't be hard to find a pilot if that is the case.)

Would "a happy person with [only] PPL and IFR ratings" even know how to operate a 737-800? Sure, much skill is probably transferable, especially if you're used to a glass cockpit and maybe even have a multi-engine land rating (or your local equivalent), but even ignoring little details like, say, the FMC, there's for sure a whole lot more of everything. You might want to look up XC-VMC for a cautionary tale.

@aCVn I dont think it has something to do with the flight training. As I see all they did was failing to turn the speed knob or relying too much on the autopilot which slowed down the plane slowly compared to the manual pilot control.

But you sure need to know the control and how aircraft feels, when to flare etc. It’s much harder than switching from Prius to Humvee.

In addition to a type rating, you cannot fly a 737 without a commercial pilot's license and 1,200 flight hours. Further, your flight and maintenance operation must be certificated by the FAA. You'll need FAA approved opspecs, flight manuals, pilot training and testing, a drug test program, hazmat program, a designated safety manager, and more.
Aircraft with 20 or more passenger seats, or 6,000 lbs payload capacity must be either flown under Part 121 air carrier rules or else they fall under Part 125 regulation. Except for limited circumstances, they cannot be operated under Part 91 (exceptions fall under Subpart F). Because your party isn't a training flight, you don't own the plane, it isn't a sports team, etc., you are under Part 125.
Once the aircraft is large enough, there is no longer a distinction between private and commercial operation, Part 125 covers commercial operations short of common carriage. Even if you're operating an aircraft privately, you have to comply with commercial level safety requirements.

Is the 1,200 hours related to a frozen ATPL?  I'm guessing a cargo 737 with no passengers wouldn't require any sort of ATPL so it would be a type-related requirement???

@DaveGremlin It's not related. You need 1500 FH for an ATPL. The need for the ATPL depends on the type of operation. For example, UPS and FedEx are common carriers, so they fly under 121, so a ATPL is needed.

There are truths in this answer, but it confuses merely flying the plane, with flying for compensation and running a charter company.

@MichaelHall No, you missed the entire point of this answer. For large jets, these become all the same. Part 91 does not generally apply to large jets and neither does 135. If you think different, write you own answer.

@MichaelHall This article explains the history. FAA wrote Part 125 to cover everything, allowing ad-hoc exemptions and ended up writing some specific cases into Part 91. If not in one of those cases, Part 125 applies. (The scope limit proposed in the article of 125 never happened and blanket exemptions are no longer issued)

I did write my own answer, but you have shown me the error of my ways and I deleted it.  I wasn't familiar with Part 125, I appreciate you straightning me out!  (downvote changed to upvote...)

You would most certainly need a type rating to fly a 737. Any turbine-powered airplane or aircraft gross weight greater than 12,500 lbs (5.67 t) requires a type rating.
In this case, you will need quite a bit of extra training to fly a 737 and need to pass a practical test to earn a type rating.

§61.31 Type rating requirements, additional training, and authorization requirements.
  (a) Type ratings required. A person who acts as a pilot in command of any of the following aircraft must hold a type rating for that aircraft:
(1) Large aircraft (except lighter-than-air).
(2) Turbojet-powered airplanes.
(3) Other aircraft specified by the Administrator through aircraft type certificate procedures.
  Large aircraft means aircraft of more than 12,500 pounds, maximum certificated takeoff weight.
Part 1.1: Large aircraft means aircraft of more than 12,500 pounds, maximum certificated takeoff weight.

What about ATP?

Also, I doubt that you could legally fly a 737 with just a single pilot.

@jamesqf I also remember something about IFR only being allowed if there is an copilot with you.

ATP also requires type ratings.

@JonathanIrons IFR doesn’t require two pilots.  The operation or aircraft may require two pilots.

@wbeard52 I'm not sure what you mean, but I don't think there any requirement to have a type rating in order to get an ATP. You can get a single-engine ATP in a light single if you really want to.

Type ratings are tested to ATP standards, so if you have the hours, you might as well pick up your ATP while you're at it.

Yes -- the most common case is with people who own their own bizjets/VLJs, say a Citation Mustang; that requires a type rating, even if you're just a PPL/IR flying it

Does turbojet only refer to turbojet as opposed to turbofan?

Turbojet and turbo fan are interchangeable for this regulation.  Turbo prop would be different.

authors: Vladimir F Героям слава


text:
What is the two-person cockpit rule, as of February 2020?
In the comments to the accepted answer on this question, there is some conflicting information about the current regulations around the 2 person cockpit rule.
I was under the impression that there must be 2 people at all times after Germanwings Flight 9525.
What is the rule currently (Feb 2020) in both EU and the U.S for minimum number of people in the cockpit?

As for the EU, EASA has published SIB 2016-09 which states that: (emphasis mine)

CAT.OP.MPA.210 of Regulation (EU) No 965/2012 stipulates that flight crew members required to be on duty in the flight crew compartment shall remain at the assigned station, unless absence is necessary for the performance of duties in connection with the operations or for physiological needs, provided at least one suitably qualified pilot remains at the controls of the aircraft at all times.
In such cases, the Agency recommends operators to assess the safety and security risks associated with a flight crew member remaining alone in the flight crew compartment.
  This assessment should take the following elements into account:
1) the operator’s psychological and security screening policy of flight crews;
2) employment stability and turnover rate of flight crews;
3) access to a support programme, providing psychological support and relief to flight crew when needed; and
4) ability of the operator’s management system to mitigate psychological and social risks.

In other words, it is up to the individual airlines to decide if they want to implement a rule requiring two people in the cockpit at all time. It is not a legal requirement.


text:
Do I need complex endorsement in each class or type of aircraft?
I have experiences with PA28R and got a complex endorsement from my instructor.
Now, I am working on multi add-on and flying DA42 Twinstar.
Do I need another complex endorsement that specifies the class and the type of the  aircraft for DA42 checkride?

You only need one complex endorsement under FAA regulations,

§61.31   Type rating requirements, additional training, and
  authorization requirements.
(c) Aircraft category, class, and type ratings: Limitations on the
  carriage of persons, or operating for compensation or hire. Unless a
  person holds a category, class, and type rating (if a class and type
  rating is required) that applies to the aircraft, that person may not
  act as pilot in command of an aircraft that is carrying another
  person, or is operated for compensation or hire. That person also may
  not act as pilot in command of that aircraft for compensation or hire.
(e) Additional training required for operating complex airplanes. (1)
  Except as provided in paragraph (e)(2) of this section, no person may
  act as pilot in command of a complex airplane, unless the person has—
(i) Received and logged ground and flight training from an authorized
  instructor in a complex airplane, or in a flight simulator or flight
  training device that is representative of a complex airplane, and has
  been found proficient in the operation and systems of the airplane;
  and
(ii) Received a one-time endorsement in the pilot's logbook from an
  authorized instructor who certifies the person is proficient to
  operate a complex airplane.

In your case a class rating is only required for the "multi" aspect of the DA-42 as the DA-42 has no type rating.
The FAA further more defines complex aircraft as

Complex airplane means an airplane that has a retractable landing
  gear, flaps, and a controllable pitch propeller, including airplanes
  equipped with an engine control system consisting of a digital
  computer and associated accessories for controlling the engine and
  propeller, such as a full authority digital engine control; or, in the
  case of a seaplane, flaps and a controllable pitch propeller,
  including seaplanes equipped with an engine control system consisting
  of a digital computer and associated accessories for controlling the
  engine and propeller, such as a full authority digital engine control.

No part of this definition stipulates how many engines the aircraft has.


text:
Can I log simulated instrument time in a simulator as a CFII?
I started working as a flight instructor and have a couple of questions about logging sim time as a CFII:

If I fly a sim session with my student can I log the sim time as dual-given time?
If the sim session was conducted in simulated IMC, can I also log that for myself as simulated instrument time? Or does it only count for the student?

Why What do you put a hood or foggles on in a Sim when it can simulate IMC already?

Logging sim time as an instructor has no value for additional certificates, ratings or currency reasons.

Somewhat related https://www.reddit.com/r/flying/comments/7rex51/why_arent_their_sims_in_busy_metropolitan_areas/dswej7y/

You can log anything you want, whether or not it counts towards something is entirely different. See Logging time in a simulator. It says as a CFI you can log it, however you should log it separately from other training (or make it clear in the entry) that you are using an ATD.

Closely related, maybe a dupe?

Please specify what jurisdiction you are asking for

A Level C or D Full Flight Simulator (FFS) can be used for all training required for an initial type rating, a 61.58 check, an IPC, landings required to maintain landing and instrument currency. In fact, so long as it is not (in most cases) your first type rating, you can fly a Level C or D sim, get certified and then walk out to the airplane, load it up with PAX and go flying, legally while having ZERO actual flight time in the actual aircraft.
So I would say yes you can log Dual given in a flight simulator, but you cannot log that time as flight time.

Level D is zero flying time, Level C is not.

That is not correct @Koyovis. We have a Level C sim and there is ZERO flying time required to fly the actual aircraft unless you do not meet the 61.64 requirements (same as Level D). This is true for all Level C simulators certified under Part 60 in the US.

Yes indeed, Level C has zero flying time for what it is certified for. But it is not certified for all of the curriculum, if it was it would be a Level D.

Once again, incorrect @Koyovis. Level C and D have nothing to with the curriculum. We can do absolutely everything in the Level C that we can do in the Level D. The primary differences are 1) Visual Systems, 2) Motion Systems and 3) Audio Systems. Level D is a more high fidelity version of the two. We use the identical curriculum in both sims. This is based on the US FAA part 60 standards, I am not sure about other countries.

Why don't you check FAA 14CFR 60, requirements for Full Flight Simulators, Appendix A. In a Level C you cannot train for situations that are not modeled. Requirements applicable to Level D only:
2.k. The aerodynamic modeling in the simulator must include:
(1) Low-altitude level-flight ground effect;
(2) Mach effect at high altitude;
(3) Normal and reverse dynamic thrust effect on control surfaces; (4) Aeroelastic representations; and (5) Nonlinearities due to sideslip.

5.f. The simulator must provide characteristic motion vibrations that result from operation of the airplane if the vibration marks an event or airplane state that can be sensed in the flight deck.
7.d. The simulator must provide realistic amplitude and frequency of flight deck noises and sounds. Simulator performance must be recorded, compared to amplitude and frequency of the same sounds recorded in the airplane, and be made a part of the QTG.

@Koyovis - We operate a part 142 school utilizing Level C and Level D simulators and have for the last 12 years. Every certification that we can do in our Level D simulator we do in our Level C simulators. This includes Initial Type Ratings, ATPs, 61.58s, 135.293/297 rides, etc. Flight Safety, SimCom and SimuFlight all have Level C simulators that they do complete initials in as well. I am not sure where you are getting your information, but it is incorrect. Call your local FSDO and ask them, or better yet, call FSI and ask about a CE500 initial in Long Beach in their Level C sim!

@Koyovis - My apologies - You are correct in that if a Level C simulator is built to the very basic standards of Part 60, it would not meet the requirements for a full type rating, they could do 80% in the sim, the rest in an aircraft. However, most of the Level C sims under the control of the NSP meet all the necessary standards to do everything in the sim. We have a Level C sim certified Level C but approved by the NSP to do 100% rides and we were certified under the (then) new Part 60 standards. The sim is NOT a Level D and we CAN do full certifications with no aircraft time necessary.

@ Richard interesting, what aircraft type is it?

@koyovis - It is a CJ1. List of all FAA certified sim are here


text:
ENGINE OIL SYSTEM SERVICING IN A318/A319/A320/A321 - ENGINE IAE-V2500

12-13-79-610-011-A - Check Oil Level and Replenish.
Reason for the Job:
This task gives the instructions necessary to fill the engine oil tank
if the oil level has decreased during normal engine operation. [...]
(A). Check the engine oil level.
(4) Servicing is not required prior to departure if the engine was serviced on arrival or the oil
tank sight glass shows a minimum of 23 quarts or the cockpit
indication shows a minimum of 19 quarts and predeparture walkaround
checks confirm no oil pools/drips from drain mast. [...]
(B). Fill the engine oil tank - Gravity Filling:
(2) Make sure that the oil level sight glass shows FULL.
NOTE: Do not fill the oil tank past the sight glass FULL level. Filling to tank overfill will result in excess oil, leading to amber
cross indication warnings and service disruption.

Question: Why is there a difference in requirements in paragraph (A-4) and (B-2)? Whichever is correct?

When you check the oil on your car:

If the oil is above "ADD" line, you don't have to add oil for your next trip as long as the engine isn't obviously leaking. There's enough to get you to the next opportunity to check it, based on normal allowable consumption rates.
If the oil is below the "ADD" line, don't just add enough to get it above the ADD line, fill it all the way, being careful not to overfill.

The AMM task is a fancy version of that.

Sorry, this AMM reference For Aircraft..

Yes I know.  I was explaining the logic of the maintenance Task. When replenishing, the airline's procedure is fill it all the way because partial fills will just cause more unnecessary servicing maintenance later.  Part A is based on the allowable minimum to get you to the next check interval.

I don't see a difference.
(A) prescribes the check conditions that determine whether (B) has to be done.
IF

(

the engine has been serviced on arrival, OR
the oil sight glass shows at least 23 quarts, OR
the cockpit indicates at least 19 quarts

)
AND the engine is not leaking oil from the drain mast

THEN no service is required.
ELSE perfom actions under B

Thinks, this good Answer.

Hello Marwan, welcome to aviation.stackexchange. If the answer solved your problem, you can accept it by clicking the tick mark below it.


text:
How much pressure do boost and jettison fuel pumps produce?
What is the pressure output of a (boost) fuel pump on a Boeing 767 and/or 777, compared to a heavy-duty jettison fuel pump.

I looked up a cannister boost pump and jettison fuel pump on the Eaton website and found a cannister boost pump for the 747 that puts out 28,000 Pounds Per Hour, and a jettison pump also for the 747 that puts out 40,000 PPH.  Safe to say jettison pumps generally have a higher output than engine boost pumps, for obvious reasons.

This answers volume; the question asked about pressure. Although I'd agree that especially for a jettison pump, PPH matters more than PSI.

@RalphJ depending on the type of pump PSI doesnt matter, if the pump is positive displacement (which the unit of PPH seems to imply) the pressure is a result of the system around the pump not the pump itself


text:
How can I convert a SACAA (South Africa) AME license into a Belgium (EASA) licence?
I have a SACAA (South Africa) AME license and would like to convert it into a Belgium EASA licence part 66. What are the steps to follow?

Have you asked if South Africa has bilateral agreements for AME licensing reciprocity with EASA and/or Belgium?


text:
What aircraft (real or fictional) does this look most like?
I just finished building a foam board plane. I did not follow any plans and this is just me being stupid and making a plane that I hope will fly. pic below.

Its a flying wing with a bit of dihedral, vertical stabilizers on either end, small elevators, and a rudder. I have not yet flown it due to bad batteries, so I don't actually know if it flies yet.
What real or fictional aircraft does this look most like?

I'm inclined to close this as opinon-based, as the aircraft-identification tag is to match photos/models of real aircraft to their "sources". As this lacks a source, I don't see how the answer would not be matter of opinion.

@Ceramcmrno0b Is the aerofoil cambered or symmetrical? If it is cambered, i.e. with more of a hump across the top than underneath, then it will need a much larger elevator trimmed to a significant "up" angle at the rear, and the CG moved forward to match, to fly stably.

It looks just like the fictional one in my mind.

I would say it comes closest to the Backstrom EB-1 Flying Plank, a tailless glider designed in the 50s.  The rear control surfaces are doing the job of the horizontal tail for pitch control and you will need some UP deflection at their "neutral" position to get it to not dive straight into the ground as soon as it's on its own in flight.  Then you have to find the right spot for the C of G.
Being very short coupled, you will find that the C of G range in which it will fly, if it will at all, is very small and it will take some experimentation to find a CG location where it is stable and controllable at the same time, and you should probably do tests by just throwing it into glide before trying to fly it with the motor.
In the RC world, all kinds of weird configurations and shapes will work that won't with full size airplanes (like flying lawnmowers) so it should be possible to get it to fly ok with lots of tweaking.  Check this page out for some tips on designing flying wing model aircraft.


text:
How do I keep the neighboring Remote Control Airfield from flying over my property?
I live in the North Georgia Mountains. The neighboring remote control airfield was put in front of my house where my mountain view is. I have no issue with them flying over their lease, just not over my property and in front of my view. I have approached them to stop, but they refuse.
Do they have the right or can I have them served for trespassing?

This is a tricky one, for starters we would need to know where you live. Generally people are allowed to fly over private property if they are not causing disturbance. This might vary depending on national legislation. Surely the rc pilots are bound by several laws and regulations, general and specific. If nothing else helps and buzzing continues, you should contact local law enforcement

I live in the North Georgia Mountains. They have leased the field next to mine. I have asked them not to fly over and disturb my mountain views. They have crashed planes in my fields and left gates open retrieving them. Just want my home and property left alone. Really not trying to be a jerk. I have tried being respectful with rudeness back.

@MikeVandegriff Thanks, I included the location in the question. I'm sure someone who is more familiar with FAA regulations than me will be able to tell you the rules for overflying your property. If you are also asking about trespassing (when entering your property to retrieve crashed planes), you should ask that on Law.SE. Here, we will only answer about aviation regulations.

I guess my question is "do individuals have the right to fly over private property. It was my understanding, if they do not have permission, they can not. Everything I have read says you must have permission. I don't want to go to the courts, just have my private space respected. The same any land owner would want.

When you say "in front of your view", it's a little unclear whether or not you are also trying to limit how high they fly over their own property.  I'm guessing not, but perhaps the question would be clearer if you simply deleted all references to the view?

@MikeVandegriff Edit your Q to add trespassing on your land (not just sky) since that may give additional legal avenues to consider.

Send the club a nice, friendly note and let them know that you appreciate them continuing to fly their aircraft over your property, as it is a handy, low-cost way for you to test and practice with the anti-aircraft batteries you've recently installed. (Only somewhat sarcastic...)

I'm surprised that all the answers and comments so far have been about resorting to laws, other higher authorities, or anti-aircraft batteries, and that nobody has suggested being nice.
When you say that you approached them to stop and they refused, that sounds like you went and talked to people flying their RC planes.  Presumably the RC airfield is leased by a club, which is probably legally organized as a non-profit corporation, which therefore has a board that meets regularly according to bylaws.  In ordinary times I would suggest finding out when the club board meets, and paying them a visit.  (With the pandemic stalking the land you're probably better off telephoning the club president or other club officer.)  If you appear at the board meeting and identify yourself politely and state reasonable concerns without accusing anyone personally, then I would think most club boards would take your concerns seriously, raise the issue with the rank-and-file club members at the next regular meeting, put a strongly-worded notice in the club newsletter, and give you telephone numbers of several board members to call in case you have any more trouble.
Most clubs devoted to any hobby just want to pursue their hobby in peace, and in order to be left alone they need to be good neighbors, and so that's what most clubs try to do.  It shouldn't be hard to get people to not fly over your property and close gates after they retrieve planes that accidentally came down on your land.
Then there is your demand that they not fly planes in your view.  Are planes over their field in your view?  In that case your demand may be neither legal nor reasonable.  (Please know that I'm no lawyer.)  Even so they may be willing to negotiate if asked nicely, and for instance offer to fly only three hours a day for two days a week just to avoid trouble.

The USA's national organization of aeromodelers advises pilots on page 4 of its safety guide:

It’s important that you respect the privacy and property of others and be aware of your surroundings. What might seem like a cool flight path to you may be a nuisance or perceived as invasion of privacy by others.

If they're an organized club (likely, as they're leasing their field), then ask them to follow these AMA guidelines;  if they don't, complain to the AMA.
If they're not an organized club, complain to the AMA anyways.  The AMA wants all radio-control pilots to behave courteously.

I would start with your township to see if there are any bylaws in that regard, then check with the county, then check with the State.
Barring that, your best bet would be to approach the owner of the property they are renting from and threaten to sue over loss of enjoyment, or have your lawyer send the owner a letter to that effect. If the RC group has some sort of organized or incorporated entity, you also might go after that.

I think attacking this from an aviation regulation standpoint would be very difficult.  The aviation authorities are hesitant to start naming specific property rights for air over property as the sky is public domain and the height of structures on property can vary significantly.
If they have cameras on those drones and they are recording, you might have better luck with pushing back on them recording without consent in a place that isn't open to the pubic where you have a reasonable expectation of privacy.
You've asked verbally and they've ignored you, so you should hire a lawyer and see how they can help you.  Perhaps a formal cease and desist letter might make them be more courteous about your right to privacy on your private property.
Also, those drones need to be operated in a line-of-sight from the operator, so if you think there is no way the person at the RC airfield can see the drone with their own eyes from that field, then I would take video or photos of that position so you can demonstrate that they are violating the line-of-sight regulation and pass that along to a legal professional for assistance.


text:
Do any RAF helicopters have skids instead of wheels?
Are there any current, or Cold War-era, Royal Air Force helicopters fitted with skids as standard?
I seem to recall hearing, when I served, that RAF helicopters only ever had wheels, whereas skids were the exclusive preserve of the Army Air Corps.
This related answer says that the choice "seems to be that they are chosen based on the mission profile of the helicopter as well as the size to some extent." But, in my experience, both the RAF and the AAC support infantry operations in fairly equal measure, and the RAF Wessex and AAC Lynx have fairly similar weights.

Prior research?

Look no further than the Defence Helicopter Flying School, which operates at RAF Shawbury, which uses (or has used) at least 3 helicopters equipped with skids:

Westland Gazelle HT3
Bell Griffin HT1
Jupiter HT1

In addition the current list of active RAF aircraft lists the Bell 412 (note the Army Air Corps use the Bell 212)
Finally an historic list of RAF aircraft lists the Bell H13, the Eurocopter AS350 and the Eurocopter AS355.


text:
What is the make and model of this biplane?
This photo is of one of my friend's great grandfather:

We wish to commemorate a museum in his name as he was a highly regarded person in his area, so we wish to show this photo in the museum with details of the plane.

A bit more information about the photo may help. Approximately when was is taken? Do you know the location?

It's a De Havilland DH.83 Fox Moth

 Source Wikipedia. Photographer:  Chris Finney
With a bit of image contrast and brightness modification, the registration can be read on the underside of the wing: VT-AEA.
VT is the registration prefix for India since the 1930's
The historic registration can be found on www.airhistory.org.uk and here.

Registr.
Type
Serial #
Reg. History
Owners
Date
Cert. #
Fate

VT-AEA
DH.83 Fox Moth
4043

The Bombay Flying Club Ltd
01.05.33
173
Reregistered 6.12.37

VT-AEA
DH.83 Fox Moth
4043
VT-AEA
GB Keshein, Bombay
6.12.37
173/2
Reregistered 1.2.38

VT-AEA
DH.83 Fox Moth
4043
VT-AEA
Air Services of India Ltd, Bombay
1.2.38
173/3
Cancelled 10.7.41

The aircraft was first owned by the Flying club of Bombay since 1933, then briefly by G.B. Keshein in Bombay and then by Air Services of India until 1941.

Just had to comment to say what a wonderful answer this is.  You could have stopped at make and model, but you chose not to; there's heaps of detail but it's still concise.  +1.


text:
What are these components in a DHS/CBP Predator drone?
In the following diagram showing the "DHS/CBP UAS Platform Configuration", what are these components and what are they used for?

PPDM
SPMA
RCM
RVT encoder

PPDM is Payload Power Distribution Module
SPMA is Sensor Processor Modem Assembly
RCM is Rabbitcore microprocessor Core Module
RVT Encoder is a Remote Video Terminal Encoder
As for what they do, that is at least For Official Use Only. You could always submit an FOIA request.


text:
How to determine the RPM of the rotating shaft of an A320 PTU?
The A320 PTU has an in-line variable displacement pump on one side and a bent-axis fixed displacement pump on the other connected directly by a shaft.
what would be needed to know how fast the shaft turns during PTU operation?

From a pilot's perspective, the answer is "who cares" (either the PTU works or it doesn't, and that rotation rate isn't directly observed nor influenced from the cockpit). From the designer's perspective, it probably was an interesting number, years ago.  From a mechanic's perspective, it needs to match whatever is prescribed in the maintenance manual, or at least the output needs to be within limits. Can you explain why such an esoteric number is of interest?

@Ralph J, I am no longer surprised, but more concerned, by the number of esoteric Airbus A320 specific questions we get here.  Do the operators not train their people in where to go for needed information so that they have to turn to internet boards to do their job?  Or is there something about the A320 that is just so fascinating that aviation enthusiasts crave trivia like this?

@MichaelHall for all we know it could be a homework exercise or an exam question for A320 mechanics.

@DeltaLima, I think you are agreeing with me...  But either way, if it was homework shouldn't you seek the answer in approved manuals?

@MichaelHall my theory is that an increasing number of people can't absorb information from a well structured document anymore, unless that document has been indexed by google. The "art" of reading a document index and finding relevant sections is getting lost. As a consequence people turn up here with questions to which the answer is written in the book next to their keyboard. That then begs the question, are Boeing maintenance manuals easier found on the internet than their Airbus counterparts.

Not sure why we need to diss other people's questions.

Source: eaton.ru (PDF)

From an A320 systems design document (own work from published on-line data):

Power Transfer Unit (PTU) Eaton MPHV3-115-1C
The PTU is a double hydraulic pump mounted on a common axis, one side connected to the Green hydraulic system and the other to the Yellow hydraulic system. This enables the Green system to be powered by the Yellow system and vice versa, without hydraulic fluid transfer between the two systems. The PTU enables the gear to be retracted upon engine 1 fail, and for the LH elevator to be powered upon engine 2 fail.
The PTU has the following characteristics:

Each pump can function as a hydraulic motor for powering the pump at the other side.
The Green side pump is a fixed displacement bent-axis type, delivering max. 90 l/min on the Green side and costing max. 120 l/min on the Yellow side.  Delivered flow is a linear function of pump rotational speed.
The Yellow side pump is a variable displacement type, delivering up to 50 l/min on the Yellow side at a cost of 60 l/min on the Green side.
The PTU switches ON automatically when one side has a pressure that is 500 PSI lower than the other side. It switches OFF when pressures are close to equal.
PTU function can be inhibited from a switch in the cockpit.

Source: aircrafttechnic.com

The PTU shaft RPM can be determined from the following:

Powering the Green side: a linear function of Green system delivered flow.
Powering the Yellow side: also a function of delivered Yellow system flow, although not linear. The pump is a variable displacement one, which usually ramps up to its standard operating RPM and then regulates displacement from a pressure feedback loop.
A sound measurement, in which a dominant frequency will occur of the pump pistons rotating. The PTU sound is a cue that is recorded and reproduced in Level D simulators, frequency analysis will reveal the pump piston frequency.

There will be dynamic effects in RPM to to changes in power delivery.

@ymb1 The text is own work, from a simulation software design report.

The shaft speed is dependent on the flow rate through the fixed displacement side of the PTU. I am not sure what the size of the A320 PTU pumps are, but it will have some fixed amount of volume per revolution, such as 0.9 cubic inches (14.7 ml) per revolution. Therefore, if you know the flow rate into that pump (Green Side) you can easily calculate to the shaft speed.
Again, I am not familar with the A320 system specifically, but the PTUs I am familiar will all have a flow regulator upstream to control the maximum flow rate (and thus speed) of the PTU.

If you are not allowed to attach the measuring device to it, the two unobtrusive methods are by sound or by video.
Measuring by video would require the device to be visible, have some surface features to determine some particular rotation and the possibility to make probably video recording while in operation. The recorded video can be split into individual frames in the simplest case just estimating the rotation visually, as the time interval between the frames would be known. Otherwise, tools like OpenCV or fast.ai may help to analyse the images automatically. But these methods are limited by the number of frames per second you can capture. Most of the cameras would only do 30 frames per second or about but much faster cameras are available if you look on purpose. But the method can also capture slow or irregular movements.
Another approach is by sound - record the sound and plot the windowed spectrogram of recording. This can be done with less access possible, and work with higher frequencies, as long as the rotation sound is loud enough. Of course it will be a strong band from the engines on the spectrogram but it may fall far outside the reasonable frequency range of this "barking dog".

Sounds like a credible answer, but do you have any references?  Does this come from the AMM?


text:
Why is this equation for TAS only valid for subsonic flow?
I came across the equation for calculating True airspeed (TAS) on Wikipedia:
$$ \text{TAS} = a_0 \sqrt{\frac{5 T}{T_0} \left[ \left( \frac{q_c}{P} + 1 \right)^{2 / 7} - 1 \right]} $$
But this equation is apparently valid for only subsonic flows.
Why is that? Does this have something to do with pressure?

Because you didn't read the text in the Wikipedia page above that equation ;-)
That equation works for subsonic flow only because you have replaced the Mach number of the original TAS formula:
$$ \text{TAS} = a_0 M \sqrt{\frac{T}{T_0}} $$
with the formula of Mach number for subsonic flow:
$$ M = \sqrt{\frac{2}{\gamma - 1} \left[ \left( \frac{q_c}{p} + 1 \right)^\frac{\gamma - 1}{\gamma} - 1 \right]} $$
which exploit the simple form of Bernoulli's formula, working only for incompressible flows, i.e., subsonic flows. Check the Mach number and the Bernoulli formula pages for further details.

Actually I have not gone through the derivation of this equation and how it exploits the basic form of Bernoulli's equation. The formula was just mentioned under high speed flow and yet it was mentioned (for subsonic flows). I'll look into this. Ty

Probably because Supersonic flow is totally different than subsonic flow. Subsonic, the movement of one molecule, (just from it's kinetic motion due to temperature), is faster than the flow velocity, so the effects are felt by other molecules downstream before the flow reaches them. This is in fact the speed of oscillations in the fluid, i.e., the speed of sound. The molecules in front of the flow therefore, move away from the ones pushing them before the flow reaches them. The flow is incompressible.
In supersonic flow, otoh, the flow is faster than the speed of the molecules, so the molecules don't feel the effects of the flow until the flow itself reaches it. The flow is, therefore, compressible, since the molecules "bunch-up" in front of the flow. This bunching up is in fact the shock wave created by the Supersonic flow.

Here we read that sub and supersonic flows are different, and see a comparison of their characteristics. But the explanation of how the above invalidates the equation is missing

Exactly..I am aware about those characteristics too. But that doesn't answer my question. Thanks anyways.

Hey, Why is the formula for Chemical reactions different than for Nuclear Reactions? They are different, so the formulas are different. You didn't ask why either the subsonic formula is as it is, (how it is derived from the physics), or why the supersonic formula is as it is, (how it is derived from the physics), you just asked why they're different.

I did not ask why they are different. I asked why the formula is no longer valid in the other case. Never have I asked why are the two flows different and respective characteristics. Anyway the question has been answered. Thanks

Well, you're welcome, but the answer you selected doesn't answer that question either. Simply showing the other equation doesn't answer the why. The only thing that answers the why as you seem to mean it is to describe the derivation of the two equations, which would be based on the physics - i.e., the characteristics of the two different flows.

... and putting the derivations in this forum would be overkill. I assumed that there would be enough understanding to realize that pointing out how the characteristics of the two flow are different would make it clear that that the formulae derived from those characteristics would have to be different.

Both formulae, are, necessarily, derived form Navier-Stokes, which applies to ALL fluid flows. But in their respective derivations, at some point (I would have to go back and research to find where), the two derivations would necessarily have to make different assumptions, about the very characteristics I mention in my answer, (among others).


text:
Can UK CAA modular exams done before Brexit be used towards an EASA license?
I am stuck with some EASA basic modules (Form 148) and some UK CAA modular exams.
Now I want to apply to get an EASA B1.1 license but the problem is German aviation authority (Luftfahrtbundesamt) is not accepting the modules by UK CAA even though the exams were held before the Brexit.
Can anybody recommend me something from where should I apply for EASA B1.1 license? Or do I have to re-appear in the modules given by UK CAA?


text:
Why are aircraft not equipped with nose cargo doors when being converted from passenger to cargo variant?
I'm trying to find any substantiation / design justification why none of the OEM/STC holders are able to provision nose cargo doors on A321 / B757 / B767 / B777 fleet as part of P2F (passenger to freighter) conversions.
I'm sure there would have some discussions/presentations on this, appreciated to guide with reference.

The obvious answer would be that such a modification would be too expensive compared to the potential benefit it adds

One consideration on the A321 / B757 / B767 / B777 fleet: The cockpit is in the way. If you look at aircraft with nose cargo doors (747, C-5, An-124, An-225) the cockpit was placed with consideration for fitting a nose cargo door. The A321 / B757 / B767 / B777 fleet weren't.

The simple answer is there isn't the space. The problem with nose cargo doors is the cockpit. The cargo door must be high enough on the aircraft to line up with the main cargo hold to be useful. On larger aircraft designed with this in mind from the start, (747, C-5, An-124, An-225) the cockpit is placed in a location above the main deck so that the cockpit does not obstruct the path from the main cargo hold to the nose door.
This is specifically why the 747 was built as a two deck aircraft with the hump. When the 747 was originally being designed, Boeing thought that there was a significant risk that supersonic aircraft would fully replace the market for long distance passenger aircraft. So they wanted their long distance subsonic design to be a very competitive bulk freight aircraft in that scenario so it would still make money. Because of this they wanted to be able to fit a nose door, so they needed to put the cockpit on a raised deck, which left them with the hump deck for aerodynamic reasons.
However, on current generation narrow bodies, they simply aren't tall enough to do this. They are single deck aircraft, with the cockpit located directly in front of the main payload deck.

How about than following concept of Swinging Tail, same like Dreamlifter.
This should address the problem of Cockpit location.

That is a different question.

and worse, the structural integrity of the airframe would be changed so much it'd need recertification as a new type, which is extremely expensive, making the entire process uneconomical. A small forward door could be handy to load containers and palletised cargo, but at the cost it's just not feasible

With all the connections between the cockpit and the rest of the aircraft, a modification which makes the cockpit swivel out of the way is way too complicated. In cases where a conventional airframe needed wide open access to its cargo hold, the tail would be made removable. The Junkers 52/1m would be one example, and the Conroy CL-44 "Skymonster" would be another. It was specially designed to ferry the large RB-211 engines for the Lockheed Tristar around.
The picture below was shamelessly copied from the Wikipedia article. Note the bulges near the tail: They cover the hinges for the sideways opening fuselage.

Regarding the presentations you desire: Those are all company-internal and not for public consumption.

Other than the answer of there isn't space, you would need to cut open the airframe. When 747 passenger planes are converted into freighters they don't have a nose door. There is obviously space but cutting up the airframe would make legally getting it in the air again virtually impossible.

But they also cut into the airframe to install the side cargo door.

And they do cut into the airframe to make the Dreamlifter.

@vasin1987 The Dreamlifter is barely legal: its certification is with the caveat that it can only carry cargo owned by Boeing which cannot be flown otherwise, unlike the Beluga which carries commercial cargo. The big technical compromises is that the Dreamlifter loses main cabin pressurization and the APU.

@Bianfable but they take a lot of care to not cut into major structural elements, which you would of necessity need to do to cut away the nose and part of the forward fuselage.

@vasin1987 plus those are purpose built aircraft, not aftermarket conversions. They're basically classified as experimentals with some extra perks, not useful for sale to the general public (or indeed at all)


text:
What are the disadvantages of a tailless ultralight design?
What are the disadvantages of a tailless ultralight design with say 20 deg swept back wings with wing tip rudders, 20-60mph, max 25 hp?
I'm not an aerospace engineer, so I stand to be corrected:
The only 2 disadvantages I can think of are:

Increased wing area/more weight/stronger spar

I understand the wing area would need to be larger as the "aerodynamic wing span" would be smaller than the physical wing span. I understand the wing only produces lift with the velocity component perpendicular to the leading edge ( which I understand would be V0*cos(radians(20)))

Possible reduced or no side slip angle.

I understand you're not supposed to side slip a Velocity aircraft as the leeward wingtip vertical tail may stall ( rudders only move outward). I understand only the right rudder deflects outward when turning right ( the left rudder acting only as a vertical stabilizer, in this case) I'm attributing this to too thin of a vertical tail airfoil ( low stall angle ) with too high of an aspect ratio. ( I stand to be corrected on all the above). I understand Velocity reduced this problem by reducing the max angle of rudder deflection.
Are there any other disadvantages in terms of stability, cross wind landing, etc?
See pic below of the Mitchell Flying Wing:

The last paragraph might better be a separate question.  Also tell us, when you give a right rudder input in a Velocity, which tip-rudders move in which direction? Some aircraft with tip rudders move the rudders only inwards or only outwards.  If you don't know the answer, maybe grounds for yet another question.

It seems Not clear....helicopter,plane?

Yes, I meant vertical. Corrected.

The answer has to be yes there is a tradeoff but-- I don't have more details ready at present.  The Aerianne Swift ultralight sailplane is one example of a successful aircraft along these lines.

When we designed the SB-13, we also thought that it's not so much different from a regular layout. Boy, were we wrong.
It starts with ground handling: Regular aircraft have some distance between front and main wheels, and even more between main wheels and tail skid in taildraggers. This makes them fairly stable in pitch on uneven surfaces. When both wheels are close together because there is little of a fuselage to space them apart, every bump on a grass field translates into heavy pitching. This is annoying.
It gets worse once you lift off: The little pitch damping (now I am talking of the aerodynamic sort) means that every gust makes the tailless aircraft enter into a noticeable short-period mode. This is normally so much damped that the pilot doesn't even notice. In a tailless plane the damping is just enough to stop the motion once a considerable change in pitch has happened. Of course, the pilot will try to steer against it, but with the unavoidable delay of a human in the control loop. That means the counter action will now make the aircraft pitch against the initial motion just when natural stability does the same, so an overshoot follows. Either the pilot suppresses the learned reflex of actively stopping the pitch motion or a pilot induced oscillation follows. This is even more annoying.
So much for the annoying stuff. The outright dangerous would be:

coupling between fast period mode and wing bending. Flutter at low speed is the consequence.
Nasty stall characteristics once the combination of sweepback and aspect ratio surpasses a certain threshold. For 20° sweep this would be an aspect ratio bigger than 7.

You are right about the larger wing area, but this actually helps to make the spar lighter since there is more height to place it in. Unless you need to stiffen the spar in order to shift its bending eigenfrequency above that of the fast period mode in your allowed speed range (plus 20% safety margin).

Significant washout, with tip downforce, can cure the stability and stalling issues. Indeed, the first aeroplanes to be certified fully stable by the British authorities, even when flown hands-off, were of this design. The drag penalties are less than expected, at least in part because the root bending moment and accompanying structural weight are reduced.

Yes, Dunne and Prandtl wing. I know. Reduces maximum lift even more

I would assume that one of the problems of GA aircraft is there is no damping/use of shock absorbers ( probably due to weight) in either a bungee chord or any other suspension system. A motorcycle has a small wheel base too, but does not suffer from this pitching. Is this correct thinking?

@Fred: I agree that the motorcycle suffers much less. The SB-13 originally had an undamped front wheel which turned out to be inadequate and got replaced by one with a damper. Still, off-road motorcycles need more damper stroke but still shake when driven over uneven ground.

@ Peter Kampf: With the SB-13, I assume the rudders were drag rudders? Is this correct? If so, why is that?  I assume a smaller moment arm ( less wing sweep) was chosen for better wing efficiency and a drag rudder creates a bigger moment than a classical rudder. Is this correct?

@Fred: Rudder deflection was -20°/+70°, so the rudder on the downgoing wing would create drag while the other would contribute side force. The 15° wing sweep were a compromise between not too much lift loss, still acceptable stall characteristics, enough tip clearance in a flare, sufficient pitch stability and enough pitch control power. Yes, the drag rudder is quite effective but you want to use it as little as possible in a glider.

@Peter Kampf: So could drag rudders be mounted on the end of a stabilator? Please see my latest post.

This has been a contentious question since 1910 and shows no sign of being settled yet. Several of your intuitions about the problems of the tailless swept wing are common mistakes.
Perhaps the best way to approach the design is "putting the tail on the end of the wing".
Some observations on its benefits:

Yes there is a greater wing area but there is no tail structure so the balance of benefits vs disadvantages is far from obvious. Although extrapolation to supersonic speeds is tenuous, we may note that most record-breaking jets have been tailless.
Prandtl showed around 1930 that sufficient washout for the tips to exert a modest downforce will actually reduce structural loads compared to a conventional wing, and NASA have recently been revisiting his analysis.
Wing sweep confers some stability in yaw. tip anhedral combined with washout and downthrust adds more. For the Dunne D.7 of 1911 this was sufficient and it was officially certified as stable.

Some observations on its disadvantages:

Rudders are pretty ineffective. The best solution is to use drag rudders - split control surfaces on the trailing edge of the outer wing, sometimes combined with the ailerons. In the Mitchell design shown, only the inner rudder is moved for a turn and it operates more as a drag rudder than as a conventional one; they can even be operated together, in opposite senses, as an airbrake.
There is high sensitivity to pitching forces, due to the low inertia in pitch. However pitch control is difficult to make effective for the same reason as rudders. Geoffrey de Havilland remarked of the DH.108 that "The sensitivity is there, but not to any great extent". But without very careful design, the end result can be a bit lively and prone to Dutch roll; famed test pilot "Winkle" Brown described the GAL 56 as the worst-handling plane he had ever flown.
Longitudinal trim is sensitive to CG and so CG range is small. The changes in angle of attack from CG changes do nothing for the pitch instabilities.
Sharper sweep helps, but also increases sideways flow and the associated inefficiencies.
It is difficult to keep the tips off the ground when taking off. had Peter Kampf and his friends (see his answer) read the autobiography of Westland's test pilot Harald Penrose, they would have been forewarned of the unpleasant ride via the Westland-Hill Pterodctyls.

And now we know why probably 997 out of about 1,000, or 99.7% of 1,000 current GA aircraft designs have a tail. Oh well.

I assume the Mitchell wing tip rudders are too low as they are in bathed in the vortex of the end of the wing, which is probably the reason the twin Velocity VTs are so high: the bottom half of the the VT acting as an end plate/winglet, the top of the rudder being more effective. Is this correct thinking?

I think the max cross wind landing of a Velocity is 28knts, about double a C172, so we know they work. :)

@Fred Not really. The Velocity has a large side area in front of the CG so it needs plenty of side area behind it to maintain stability. Handling characteristics of a given design may be a deliberate design decision or a surprise.

So why do you say the rudders on a Mitchell are pretty ineffective? This must be more than just too small a VT volume/moment, no?

The tail volume is far too small, that is the only reason. Hence Mitchell's solution of wiring them up as differential drag rudders, in which mode they work perfectly well. I have now made that clearer.

Does a drag rudder need to be at the trailing edge, or can it be a small spoiler near the wing tip in front of a 25% chorded flap hinged onto the main spar at c/4?

@Fred A small spoiler like that does create a drag moment but it also dumps lift and causes the wing to drop. These are usually referred to as spoilerons. A drag rudder does not affect lift any more than a conventional one does.

So it's just a wing tip split flap ( downward deflection only). Given the same moment arm and area as a conventional rudder, would it create the same moment?

Not quite. A simple split flap affects the lift. On a standard drag rudder the upper surface is hinged as well; both upper and lower surfaces open together to eliminate any pitch change. The Mitchell achieves the desired effect slightly differently. If you want to know more, ask a question about drag rudders and post a link to it here.


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Do motor glider pilots ever "cheat" and use their motors to thermal?
Do motor glider pilots ever "cheat" and use their motors to thermal?
I understand there are 2 types of motor gliders:

Self launching: with about 80 hp very similar to an ultralight except a lot more aerodynamic. They can self launch (takeoff) themselves without a tow.
Sustainers: with about 15 hp, they cannot self launch, but can use the motor to sustain flight to get home if they cannot glide all the way home due to lack of thermals, sinking air, etc.

I understand gliders soaring over fields spend about 20% of their time thermalling to get altitude.
Why not just put on the motor to thermal faster and spend more time gliding (assuming you're not a purist)?
Is this ever done?

See my chat posts to the Hangar Monday for one perspective on this -- https://chat.stackexchange.com/rooms/12036/the-hangar

Do yachtsmen turn on the motor when under sail to increase their speed a little bit just for fun?  Not unless they have to get somewhere in a hurry, or to get somewhere when the wind dies. Kind of defeats the point of sailing.  Soaring is simply sailing turned from a 2 dimensional art to a 3 dimensional art, by rotating the lift vector created by moving air to a vertical axis from a horizontal one.
You have to understand that the whole point of soaring is the "game" you play with the atmosphere.  You're either into the game or you aren't and a motor pollutes the game if you use it while playing, except in specific circumstances.
Most motor gliders use the motor to launch and hunt for initial lift, then once lift is found, the motor goes off and the game starts (if you're are being towed and your tow pilot is any good, he/she is also hunting for lift for you while on tow and will try to get you near or in a thermal when you get to release altitude).
In general, you will use the motor mainly to launch and find lift, then only to rescue yourself if you get caught low.  So the motor is mostly to eliminate the tug, and the need for retrieve crews if you land out, or retrieve tows if you land out on a usable airstrip.  High performance motor gliders with retractable motors have to go through a retraction/extension procedure as well, so that is another factor in discouraging motor use until you really need it.  Of course, the other problem is you're more likely to need it, because the ballast of the launch motor hurts your sink rate, like having water ballast you can't get rid of, and it's more of a struggle to stay aloft in weak lift.  But again, this is normally a late in the day gotta-get-back situation.
On the other hand, there are "touring" motorgliders, with medium gliding performance and that are meant to be usable as long-range cross country aircraft in the travelling sense, with engines and props that facilitate starts and stops quickly at any time, as well as pure soaring, and landing gears that make normal power plane airport operations feasible.  You could really call these "hybrid" aircraft.
In these cases you may well indeed use the motor to supplement weak lift if it's to help you get from A to B.  But even there, you're making a lot of noise, and it's so much more pleasant with it off, so you'll avoid running the motor when you can.  This is probably more akin to "motorsailing" yachts that are a hybrid of power boat/sail boat.
With the newest electric motorgliders, you may use the motor more to help with thermaling, but they still make a bit of a racket compared to motor off (fast turning prop) and have limited endurance, so you still would tend to avoid using it unless necessary.

Lot's of sailors use their engines much more than necessary. It just depends on what is one's mood, skill, motivation, and interest.

It would only be cheating if there are rules applied that prohibit using it, this is the case when flying competitions or logging and uploading your flight to competition web portals.
To prevent cheating, motor gliders must have loggers with a microphone, so they also log the sound level to check if the engine is running. Depending on the type of competition the engine running will make the flight invalid or split it in separate flights.
If you are just flying for fun you can use it as it makes sense for you, but engine time is expensive and the noise level is no pleasure. Also limiting is the small amount of fuel and the fact that motor gliders are only effective in a small speed range. So the most time its used to get back home, start early to avoid missing the beginning thermals or reaching areas with better weather conditions.
Touring Motor Gliders are an exception, they are mainly used with engine running


text:
Does momentum theory include deflected slipstream thrust lift at high alpha?
Does momentum theory include deflected slipstream thrust lift of a wing at high alpha?
I understand that momentum theory calculates lift due to the angle at which the air is "turned" over chord the wing.
What about wing at 30 deg alpha?  The lift should also include the downwards x component of thrust, or is this already "included" in the calculation?

Can you please post a diagram? Momentum theory usually refers to an idealized swept disc propeller and doesn't really take flow over each element into effect (unlike blade element theory)


text:
Why does the NASA X-57 need a "gust control system"?
Why are NASA's engineers concerned about gusts affecting the X-57?
I understand that NASA is recommending automatic torque based prop speed control to be used in flight but also in gusty conditions.
Source: https://en.wikipedia.org/wiki/NASA_X-57_Maxwell

The speed of each propeller can be controlled independently, offering
the ability to change the over-wing airflow pattern to cope with
flying conditions, such as wind gusts.

I understand:

The original airplane being used had a wing loading of about 17lbs/sq ft.

The X-57 has a wing loading of 45 lbs/sq ft with its new smaller wings.

The higher the wing loading, the less an airplane is affected by wind gusts as it needs much more wind velocity to generate lift. E.g. frontal wind gust hitting one wing, then the other on a lower wing loading would create much more roll.

Source: https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-109.html

High-Aspect Ratio Experimental Wing
Perhaps the most noticeable difference from the X-57’s Modification II
configuration is the development and integration of an experimental,
high-aspect ratio wing. Designed by Xperimental of San Luis Obispo,
California, the wing features a large reduction in area, with wing
loading increasing from 17 pounds per square foot to 45 pounds per
square foot.
The reduction in wing area also contributes to more efficient cruise
flight through decreasing friction drag. The final Modification IV
effort will demonstrate that the high aspect ratio wing with the
integrated high lift motor system will allow the X-57 to take off and
land at the same speed as the baseline P2006T. The aircraft will also
be less sensitive to gusts and turbulence, leading to a smoother
flight.

If the X-57 is less sensitive to gusts, why does it need a "gust control system"?
One possible answer is that the X57 needs that flow over the wings to generate lift.
I understand that the X57:

has 14 x 24" 5 bladed props
props spin at about 4,500 rpm
motors generate about 14,000W of power
stalls at about 60mph.

Entering that into java foil, the programs generates a prop exit speed multiplier of 1.6 or roughly 100mph.
See pics below

Example:
10 mph headwind, gusting to 20 mph, increase is 10mph, which is only a 10% of 100mph airflow over the wings at a stall speed of 60mph, with wings that should be 300% less affected by wind due to 300% higher wing loading.
So why does it need a "gust control system"?

Sometimes engineers do things just because they can.  (For example, does anybody actually need windshield wipers that turn on automatically when rain is sensed?)  Perhaps it is being used as a test bed for proof of concept.  Not an answer, but that would be my bet...

It would depend on the direction of gust. High-aspect-ratio wings have a lower rate of roll. Thus, an upward crosswind gust that introduces a rapid uncommanded rolling action may not be sufficiently correctable by aileron deflection alone, and may require the asymmetrical application of thrust to increase the control surface authority and lift of the lower wing.

But 45lbs/sq ft is not that high of a wing loading, compared to passenger jets at 150lbs/sq ft* ( *I'm told).

@Fred: That's comparing apples and oranges. The aspect ratio of a 747, for example, is 6.96. On the X-57, it's 15. High-aspect-ratio = Slow roll rate. Even gliders, which have a very low wing loading and very high aspect ratio, can have a problem recovering from sideslipping when a gust of wind raises one wing sharply. This is one reason they incorporate pronounced dihedral into their wing design.

Sorry. I read high wing loading, instead of high aspect ratio.

Wouldn't full span ailerons or ailerons with a deeper chord be a much simpler and safer engineering solution?

@Aaron Holmes just to benefit your good writings, adding wing dihedral makes side gust worse.  The drag balance around the CG (vertically, from the side) determines crosswind roll stability. The easiest way to do it, just like a paper airplane, is to put a light "keel" underneath.  This is the unsung benefit of ventral fins, and part of the Predator drone design.


text:
Compering between ILS / BARO-VNAV
my question concerning the Comparisons between the ILS/ Baro-VNAV approaching system
from the view points of safety, technician ( infrastructure, installation,maintenance and ..eg) relation efficiency, capability, accuracy and functionality?
thanks to your good sides..
best regards

So what actually is the question? It might help if you ask an English-speaking friend to help you write it down.

ILS provides both lateral and vertical guidance with high precision, which means aircraft using an ILS are allowed to get very close to the ground and each other without visual contact; in theory, a Category IIIC ILS is precise enough to land with zero visibility, but so far no examples actually exist.  Where ILS approaches exist, they're usually preferred.
Baro-VNAV provides only vertical guidance; it would be used for RNAV procedures in conjunction with some form of lateral guidance such as DME/DME/IRU.  Due to the pilot having to manually enter the altimeter setting and the general accuracy of altimeters, the margin of error is much higher and aircraft are not allowed to get nearly as close to the ground (or each other) as they would be with ILS.  Also, Baro-VNAV systems are known to be inaccurate at extreme temperatures (either high or low), so they aren't always available, whereas other vertical guidance systems are immune to that.
The other main difference is cost.  ILS requires both localizer and glideslope equipment on the ground for each runway served; installing and maintaining those systems is quite expensive, whereas the on-board equipment is relatively inexpensive.  In contrast, Baro-VNAV is already installed on many airliners and requires nothing on the ground, just minor modifications to RNAV procedures already being developed for GNSS-equipped aircraft.  The accompanying lateral guidance systems also already exist for other reasons, so there's little or no cost there either.  The combination allows airlines to more reliably and more safely serve the public at more airports with minimal cost to everyone, so it's a reasonable compromise for airports (or individual runways) that don't have enough traffic to justify the high costs of ILS.


text:
What is a typical Cd0 value for single-slotted flaps?
I've been having trouble finding any source for what a typical value would be for single-slotted flaps. I haven't been able to find any information within Anderson's Aircraft Performance and Design or any other resource readily available.
Thank you so much!


text:
Why commercial planes do not provide parachutes?
In case of emergency I think parachutes would be more safe than life-jackets.

Have you ever actually worn a parachute?  They are big, bulky, heavy, and uncomfortable.  They cannot be put on or removed quickly.  If you're already wearing one, it will make it difficult to evacuate the plane.  If you don't have one on already, there will not be time to put it on when an emergency happens.

Completely aside from how on earth 150 people would bail out of a pressurized aircraft, all expected to be able to jump into freefall in the first place, at high altitudes where they would be dead from hypoxia or exposure after a minute or two...
You wear a parachute when the risk of the "skydive" is less than the risk of staying with the airplane.  This risk balance only occurs when flying military aircraft (getting shot at or single jet engines with airplanes that glide like bricks), gliders (because of the midair risk in competitive soaring) and aerobatic aircraft (because of the risk of the pilot making it come apart).
Otherwise, not worth it.


text:
How much the true altitude will be lower than indicated altitude by 10°C colder?
Aproximately how many perecent the true altitude will be lower than your indicated altitude , if the temperture is 10°C colder than standard ?

It's not a linear deviation so it depends on the altitude and the temperature at that altitude.  The deviation gets worse as you go higher and colder.
Lower and warmer, the error for 10 deg is very small, but higher and colder it can be a couple hundred feet.
Everybody uses a standard table that you can find all over the place with Google.  See here on Page 33 of the General Section of the Canada Air Pilot CAP GEN (IFR approach plates for Canada)  which explains how to apply the corrections, and can also be found in the AIM.  They are only used for IFR use for correcting altitudes for instrument procedures when close to the ground, and are generally not applied unless the temperature at the airport is below freezing.

Thanks I couldn't get the image post to work and I just realized it was because I didn't convert it to jpeg.

Thanks for answering so what is 4% temperture corection for -10°

And also i found this formula in some other pages ................
4 ft for 1 degree of deviation from ISA for every 1000 ft , then 4x10 / 1000 = 4%


text:
What % of horsepower in a turbine is used by the compressor section?
If a turbine generates 10,000 shaft horsepower, I am trying to understand how much horsepower has been used to compress the air.  So the turbine that generates 10,000 hp must in fact generate 10,000 hp plus X hp for the compressor.  What is the amount 15%, 25%, or what?  Thanks for your response.

Related: How much power is drawn by a turbofan to power its own compressor?

I saw a figure for this once, and recall it was close to 75%. Obviousiy it varies over the decades of engine development that have occurred, but I think you are well on the wrong side of the 50% mark.